<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>

<body>
  <div id="app">
    <button @click="isHot=!isHot">改变天气</button>
    <h1>这天气很{{isHot?'热啊':'冷啊'}}</h1>
  </div>
  <script>
    Vue.config.productionTip = false;
    
    const vm = new Vue({
      el: "#app",
      data() {
        return {
          isHot:true
        }
      },
      watch:{
        isHot(){
          console.log('isHot被监听了');
        }
      }
    })
  </script>
</body>

</html>